Elastic parachute shroud and method of making it



Oct. 26, 1948. R. T. DAwEs E A; 2,452,228

ELASTIC PARACHUTE SHROUD AND METHOD OF MAKING IT Filed March 25, 1947 3Shets-Sheet 1 jizafinzanr' 1 91 12 5,61 5 J/jaq'eks Oct. 26, 1948. R. T.DAwES ETAL 2,452,228 v ELASTIC PARACHUTE SHROUD AND METHOD OF MAKING IT3 Sheets-Sheet 2 Filed Magch 25, 4947 hatented Oct. 26, 1948 sLAs'TicrARAcHUTE'snaoun lV IETHOD OF MAKING IT Robert T.

Dawes and Frank Taylor,

Hudson, Mass-.1,

Application Marc 25', 1947, Serial No. 737,077

This invention pertains to parachute shrouds and more particularly toshrouds which are ela's tically stretchable;

The shrouds which suspend the aviator from the parachute canopy havecustomarily been ihade from silk or other'strongtextile fiber. Whilesuch shrouds have the requisite strength, they are incapable ofsubstantial elastic elonga= tion when subjected to a suddenly appliedload. For this reason it has beenfound unsafe for aviato'rs to jumpfrom-planes travelling more than 125 miles per hour, for beyond thisspeed the sudden shock resultant from the opening of the parachutecanopy is so great as seriously to injure or even to kill the aviator orto burst the can opy; even at lesser speeds the shock is heavy andexceedingly unpleasant for the aviator.

It'has heretofore been proposed to employelastically stretchable shroudscapable of substantial elastic elongation, for example 100% or more Whensubjected to a suddenly applied load,"thus distributing the applicationof the decelerating force over a substantial interval of time andrelieving the aviator from too sudden and severe' a shock. Elasticallystretchable shrouds have further advantages am'ong them the ubstantialelimination of oscillation of the canopy after opening, so thatthe'aviator drops in a substantially vertical position and is thusideally situated forlanding; the cushioning of the impact of landing andthe quick collapse of the canopy in landing; while steering of thedescending parachute in ay' bejaccomplished with less danger ofentanglem'ent of the aviator in the shrouds. 7

While elastically stretchable shrouds hav'the above advantages (at leastfrom the theoretical standpoint) and while properly constructed shroudsactually dopossess these advantages in use, it has been found that forbest res'ults the shrouds must have certain distinguishing structuralcharacteristics and should be prepared in accordance with certaindefinite procedural steps.

At the present stage of rubber technique there are advantages in using aplurality or bundle of rubber threads instead of a single rubber strand29 Claims. (Cl. 87-2) to constitute the elastic core of the shroud, but

it is contemplated as within the scope of the present invention to use asinglerubber 'corestrand, providing a single strand of thedesired'strength and having the requisite elastic qualities anddurability can be obtained. Experiment has shown that when such amulti-thread elastic core is carefully made, the shroud functions asintended, but that unless care be exercised in preparing the core, itsconstitutentrubber threads may not be equally loaded when in use andthat in consequence, upon the sudden applicationof maximum loadresultant from the opening of the parachute, only a fraction of thethreads may be fully stretched. Thus some of the threads may beoverloaded, and the threads begin to break oneafter the other, untiltheentire shroud fails at much less than the'calculated load; Moreover,unless the textile casing is capable of substantial elastic elongation,iii addition to its c'apabilityf or a limited anddefinite structuralelongation, the casing may be overloaded and ruptured. One object of thepresent invention is to pro; vide a parachute shroud which is capable ofelas tic stretch to a very substantial extent, 'for exam:- pie two'hundred percent'or'more and which is reliable and long 'livedyand havinga safety face tor such that it "is capableof sustaining great andsuddenly applied loads without danger of failure. A further object is toprovide'an 'elas= ticall'y stretchable parachute shroud comprising a'core bundleof parallel rubber threads so ar= ranged that theconstituentthreadsofthe core are loaded substantially uniformly whenthecore is subjected to loading stress. A further object is to provide anelastically stretchable parachute shroud "comprising a core bundle ofparallel threads and a braided casingor jacket, the latter being capableof substantial elastic elongation when subjected to a suflicientlongitudinal stress. A further object is to provide a parachute shroudincluding a rubber elastic core and abraided casir'ig, and wherein thecore is elongated; even when the shroud is atrest (that is to sayunloaded) but is capable" of furtherextensiom-at least asgreat andpreferably far greater than that of the cas= ing. A further object is toprovide a Df mchute shroud including a rubber elastic core" and abraided casing'and wherein the core is heldunde'r low-tension" andpermanentlyelongated for example, j to approximate some its initiallength, when the sh'roudis unloaded; by the grip of the casing. Afurther objecti's to provide an elastically stretchable parachute shroudof the kind in whichrubbenthreads form a core within an elasticallystretchab-le'braided casinga'nd hav ing relatively inelastic termina1portions'for con nection with'the canopy and'har'ne'ss respectively, andwith provision for anchoring these terminal pcrtiohs so firmly to therubber core of the shroud as to avoid'aziy' danger of their separationthere from. I A further object is to provide a simple and positiveconnection betweenthe core and casing without resort to the provision,by special braiding operations, or the like, of p'oints of 'seizure'be'tween the casing and core. K A' further objectis to provide a novelmethod of making rubber elastic para-chute shrouds having thecharacteristics above noted. Other and further objects and advantages ofthe invention will be pointed out in the following more detaileddescription and by reference to the accompanying drawings wherein Fig. 1is a fragmentary plan view of a parachute shroud made in accordance withthe pres-- ent invention; i Fig.2 is a fragmentary plan viewof anassembly'of rubber-elastic threads designed to form the core of theshroud;'

tion for the next step in the operation of making the core;

Fig. 4 is a view showin the. rubber-elastic threads with end bindingsapplied, the threadsstill being under tension;

Fig. 5 is a view showing the threads with their end bindings as theyappear after the tension has been released; U

Fig. 6 is a fragmentary plan view of a completed rubber-elastic core;

Figs. 7 and 8 are a side elevation and plan view respectively showing apreferred mode of connecting two adjacent rubber-elastic cores;

. Fig.1i9 is a fragmentary side elevation showing thefinish bindings atthe ends of adjacent rubber-elastic cores;

' Fig. 10 is ,a side elevation showing a series of rubber elastic coresconnected :by relatively inelastic connecting elements to form a strandfor delivery to the braiding machine;

4 Fig. 11 is av fragmentary diagrammatic side .4 the core shall bear itsproportionate share of the load, in other words that each individualcore thread shall stretch to the same amount when subjected to the sameload. While it is conceivable that with the improvements in rubbertechnology, a single strand core may be employed for this purpose, it isnot known at the present time how tov cure a single core strand of therequisite cross sectional dimensions to insure the elevation of abraiding machine illustrating M means for delivering the unitedrubber-elastic coresunder predetermined uniform tension to the braidingpoint;

Fig. 11 is a fragmentary side elevation to larger scale, of preferredtype of tension drum; .Fig. l2 is a fragmentary side elevation showingadjacent cores and the connecting member encased in the braided jacket;

Fig, 13 is a fragmentary elevation, to larger scale and with partsbroken away, showing one "end of a completed parachute shroud;

Fig. [l -l is a diagram showing the per cent elongation of arubber-elastic core when subjected to increasingtension;

' Fig. 15 isa view'similar to Fig. 14 but indicating the. percentelongation of a stronger core; and ,v

. Fig. 16 is a diagram graphically illustrating the per "cent elongationof completed shrouds designed for supporting loads of? and 11 poundsrespectively, when subjected to increasing load.

Referring .tothe drawings the numeral l designates acompleted shroudmade in accordance necessary elasticity and length of life in service.Accordingly it is'at present necessary to use a core consisting of aplurality of relatively small rubber threads.

In accordance with the present invention, and asillustrated in Fig. 2,core threads 9 are first disposed in parallel relation and in relaxedor' untensioned condition. The number of these threads is sufiicient toprovide a core having the requiredv load-carrying characteristics, forinstance to sustain a riding load of seven pounds. Preferably therubber-elastic threads are provided in the'form of ribbon rubber such asdescribed, for example, in the reissue patent to Shaw No.,2l,977, datedJanuary 10, 1930. The individual threads of ribbon rubber tend tostretch to the same degree when the ribbon rubber strand, as a unit, istensioned. Inorder to make up the desired core, a number of strands ofribbon rubber maybe requisite, but such strands may readily be laid insubstantially exact parallel relation and may readily be loaded equally.While ribbon rubber is preferable, it is within the scope of theinvention to employ individual rubber threads, but in the latter case,

-; care must be taken in manipulating the bundle 7 site number ofindividual threads under very with the present invention, but with thecentral portion broken away to show the rubber-elastic load. Thiselastic portion 2.may, for example,

be approximately four yards long, but may vary in accordance with thecharacteristics of the rubber employed and the load to be supported, andit is to be understood that the length of the shroud may also be variedin accordance with the type of parachute and the use to which theparachute is to be put. The shroud i has the opposite terminal portions3 and 4 each, for example of the orderof twenty inches long-and whichare relatively inextensible, as compared .with the central part 2,although as hereinafter pointed out, the terminal or connecting portionsBand darecapable of substantial elastic elongation. Thecentral portion 2comprises a braided light, tension on a beam it is possible to arrangethemso that they may be drawn off in parallel relation and with almostexactly the same tension.

' Reverting to Fig. 2. where the threads 9 are shown as constituentelements of ribbon rubber, the ribbonstrands are, as above described,laid parallel and preferably they are marked with transverse'markings.H) at regular intervals, for example at intervals of 2 inches apart.

' ,Thecore-formlng rubber threads are now subjected to tension, asindicated by the arrows A and'B (Fig. 3),.until the marks Ill arespaced, for example four inches apart.

IAt suitable distances apart, longitudinally of the tensionedrubber-elastic threads, pairs of bindings H are applied. vEach of thesebindings ll preferably consists of a rubber thread wound under hightension so as to compress the bundle of core threads 9 and firmly tobind the of-theorder-ofone-half inch. The pairs of bindjacket or casing5 within which is the rubberelastic coret hereinafter more fullydescribed. The jacket E extends thoughout the length of theshroud,5-,including the terminal portions 3 and 4.

, As above noted, an essential to the successful employment ofarubber-elastic core in a parachute shroud is that each constituentthread of jacent ends-l2 of each'pair of bindings, as indicated in'Fig.5, at the lines W-Z, the cutting taking'place at. l3 where the corethreads are exposed between the adjacent ends of the bindings. Theresult of thus cutting the rubber threadsis to produce a core C (Fig. 6)comprising parallel rubber threads 9, with a binding H at each end, andallot the same effective length.

.Having' provided cores as just described, two of such cores C and(Figs. '7 and 8) are posed with their end bindings ll convenientlyspaced apart and aligned. The rubber-elastic threads adjacent to eachend binding arethen separated into groups 9 and 9 containing equalnumbers of threads and a relatively inelastic connecting cord liispassed between thes'efgroups to form a loop whose parallel runs or legsl5 are disposed at diametrically opposite sides of the end binding ll.This connecting cord l6 may, for example, be a braided cord ofsuitabletextile yarn, for instancev cotton, silk or nylon. This cord isarranged to form loops about the end bindings I l of the adjacent coresC and C respectively, and its ends are united by a knot at M (Fig. 8).The length of this double or two-ply connecting cord or strand may be,for example in the neighborhood of twenty inches (although this lengthmay be varied, as desired) in order to provi;;e the parachute shroudwith a suitable terminal forattachment to the parachute canopy or to theload-supporting harness.

Having disposed the legs id of the loop of the cord M, as abovedescribed, these legs are now firmly secured and anchored to thecorresponding end binding H by a finishing wrapping 86 (Fig. 9)consisting of a highly tensioned rubberelastic thread. The Wrapping i6embraces the legs of the loop, constrictively binding them firmly to theend binding ll. The wrapping Iii extends beyond the end of thebinding iiand tapers indiameter, as indicated at H, its smaller end embracing onlythe two-ply cord Hi. This Winding l6 forms a tapered end for the coreand also insures a firm and fixed anchorage of the connecting cord i lto the core.

Coresjc C 0 etc., are thus successively united by the substantiallyinelasticconnecting cords M, as many of these cores being, thusconnected in series as may be desired. This series of connected cores(or core strand) may then be dis-- posed in a box or other receptaclefrom which the strand is drawn oil. or preferably this series or corestrand-is wound upon a beam B -(Fig ll) having provision for applyinglight tension as the strand is drawn 01f from the beam. This series ofcores or core strand, after leaving the beam B, passes around a freelyrotatable guide roll P, preferably having a peripheral groove forpositioning the strand as it passes about the roll. From this roll P thestrand passes to a. tension ing drum D; rotation of which is opposed bya brake band having suitable means, indicated at T for adjusting it.Preferably, the peripheral surface of this drum D is covered with spongerubber S (Fig. li so that in passing about this drum the irregularstrand, comprising the relatively thick portions C, C C etc., and therelatively thin portions it, will not slip relatively to the drum.Preferably the strand, comp-rising'the conected cores, is wrappedapproximately one and one-half turns about the drum D. From the drum Dthe strand passes directly up to the former or die of a braiding machineM which may be of conventional type and which has the carriers K for thetextile yarns Y-which' form the jacket 5. During braiding, the operatorobserves the markings Ill on the core strands and adjusts the tensioningmeans from time to time as may be necessary to maintain a uniformspacing of the marks it], thus insuring uniform elongation of the coresas they are delivered to the former of the braiding machine.

The tension imposed by the drum D is such that during. the braidingoperation the cores (3,

C G etc., are elongated as illustrated, for example, at C (Fig. 11). Thecores are heldunder core rubber is held under a normal t ension by thegrip of the jacket which is between 1'5% and 25% (preferablyapproximately 20%); of that which is necessary to stretch the rubber toits elastic limit. 1

The braided jacket covers the successive cores C, C C etc., and also theconnecting cords 14, the tapered windings l6"'causingja gradualreduction in the diameter of the jacket in passing from the end of thecore. to the connecting cord M.

Fig. 12 illustrates the appearance of the jacket where it covers theconnecting'cord I, 4, the jacket being of substantially less diameterwhere it embraces the cords I4 "only than where it embraces the core; Asabove'noted, the connecting cords M are of approximately double thelength of the terminal, inelastic end portion of the shroud. After thejacket has been applied, as above described; the connectionbetween-two.corezportions of the jacket :"is severed-:midwaysbetweenvthe ends ofadjacent cores, as shown in Fig. 12 at the plane A-B, thus providing twoseparate terminal portions 4 and 47 forming the terminals of adjacentshrouds. This severing of the connecting cord with its jacketmayconveniently bedone by means of a hot Wire H, particularly h? the jacketbe formed ofnylon or similar synthetic yarn. When nylon is employed, thesevering of the covered cord by means of a hotwirefuss the fibers withwhich thehot wire contactsthera' bypositively uniting the casing-to theterminal cord of the core, and also providing 'an ,en'd finish F (Fig.13) which sealsjthe end of theften m'i'nal portion of the shroud 'an'dprevents fray- While it is contemplated that silkmay beemployed;in-"making'the iaclg f for the connecting cords t4 ploy ny n othi p rpos el'as'ti'cityof nylon whichpeifm sjthe' jacket'material toelongatest ct 1137 I ticall'y"under load to a ery fs'ubstan onthetrmhand sinegu1e rubber' elas ar'e'initially tension'ed to an amount'whic y substantially less than that necessary;tolongate them to'thehash" limit, the'fmax'imum elastic elongation of the #15 1 11 jacket isvsucl'iftha t'i-when the jacket hasextended to the fulllamount, the

rubber; cores are still within their safe stretch,

limit.

As examples'of appropriateniaterialsi tensions to be applied duringmanufacture; and, proporl tions'of-parts, the following ;;examples,are-in stanced with respect to shrouds "designed to canry. a ridingload of 7 tively.-

pounds and 1 :12 poundsi'respec Shroud 7# 11!? Riding Load RidingLoad 1. Core (a) Number of elastic thr 36. (1)) Size of elastic threads#24. Square or round threads Square (:1) Material are. (c) Totalelongation of a normal 2" length at elastic limit l". (1) Actualelongation of anormal 2 length at the braiding point and tolerit" plusor minus 56 1054 plus or minus )4.

once. i v (g) Pounds tension applied to the group of elastic threads10%1bs 1 1.. lbs. (h) Whether ribbon rubber or beamed threads RibbonRibbon.

' 2. Jacket (0) Number of braiding carriers 1.2-; 16 10. (b) Size ofyarn (denier) 210 210. (c) (1) filament 3 denier 3 denier.

(2) spun (length of staple flbers and twist) (3) t gisted-No. oi Yarns 1D (d) Material i (a) Totall elongation of jacket-forming threads: H

(1) Picks per inch:

terminal portion elastic portion in.--

(g) Tension (pounds) on jacket threads at brei rig point" (It) Totalelongation of jacket alone: I measured at 3005 tension measured atbreaking point and tolerunc 3. Text methods and results of tests (a)Elongation of a normal ((2) Ultimate elongation of same length of shroud(at 300 lbs tension) continuous (drawn) 20 to .I

10 shroud at normal riding load 19 3' 0.016 spring 1 or 6 oz. weight on2B carrier.

22% plus or minus 5% continuous (drawn). 7-ply, 2 ends up.

2% to as. 2% to 38, N ylon.

18 to 22%. 20 to 25%.

0.016 spring or 6 oz. weight on 2B carrier.

22%. 30% plus or minus 5%.

,A "0.016 spring is one made from spring wire of 0.016 inch in diameter.

signed to sustain a five-pound riding load is given by way of furtherspecific example:

7# 'Line 11!; Line 7 V Shroud, live (5) 1 Relaxed-Core-Unbraided Equiva-Inches 1 Inches pound ndmg load 2 Clent di atmectler (fulul1ated1) fi t231 2Q re esso ac e was e 4 Diameter or we walwlatedrwhw it? iititiaitiiltfifii ir" t-"3: iii.

F 15 relaxed 92 E (0) Square or round threads. Square 5 Dnimetetr oiCord, overall atmammum 166 18! (4) Material Pam e onga ion I 6 Estimatedhi k ra r 4 1132 iiiltitiifiiififffifiifii flififf ff. 18". 7 i of core.wlthm Jacket at i (f) Actual elongation oianormal 2 length maximumelongahon cord: $2 129 at braiding point 10% plus and minus 8 Diameterof core at approximately I breaking 139mt (calculated) fi (9) Poundstension applied to the group of elastic threads 5 pounds,

(h) Whether ribbon rubber or beamed g 1 threads Beamed threads. vComparison of the above yalues (7 and 8) 2 Jacket clearly shows theactual factor of safety inherent in shrouds embodying this invention;Egg gigggg gg came 5% In Figs. 14 and 15 the characteristic elongation(c) 1 filamentm; s denier.

of rubber-elastic cores made in accordance with the present invention isshownby way of example; Fig. l'representing the stress-strain diagramfor a 'Fpound shroud, and Fig. 15 showing a similar diagram for anll-pound shroud. V

Fig. 16 shows the stress-strain diagrams for completed shrouds designedto sustain a 7-pound and ll-pound riding load respectively. Comparisonof the diagrams of Figs. 14. and 15 with those oI-Fig. 16 shows theefiect of the jacket. It may be noted that while the jacket materiallylessens (2) spun or drawn 1. (3) twisted number of yarns (0!) Material(e) Trlital elongation of jacket forming -r y--- (f) Picks per inch:

terminal portion elastic portion (9) Tension on lacke omt-.. (h) (1;Relaxe Core-Unbraided Equivalent diameter (CaL) (2) Composite Cord,Relaxed Dia (3) Thickness of jacket (4) Diameter of Core (Calculated)continuous (drawn).

3-ply (3 ends up). Nylon.

cord is relaxed the elongation of the core for a given load, its (5) ggg g g ggg at effect is not pronounced until the core has elon- (6)Estimated thickness ErlaEiEtIIIIII Iozswl gated to form 200 to 240% andnot until the (7) jf g ggg g ggg gfi lack at 073 shroud is sustaining aload as great 'as the in- (8) Diameter of Com at ggggggggig tendedridingrload. i breaking point (calculated) .0543".

The following data relating to a shroud de-? contraction is impossible,but the jacket still grips the core so firmly as to prevent independentcontraction of the latter substantially. When the shroud is loaded, itis believed to respond sub stantially as follows: at first the rubbercore contracts in diameter faster than the jacket, and the coreelongates without substantial interferonce from the jacket. Theexpansion of the core under these conditions is shown in the diagramolFig. 16 where, for the 7-pound shroud, for example, elongation between120% and 240%, is

substantially proportionate to the stress applied. During this periodthe jacket also elongates, but this elongation of the jacket ispermitted by rear rangement of its constituent yarns which tend to,dispose themselves more nearly parallel to the length ofthe length ofthe jacket as the jacket decreases in diameter. These substantiallyindependent elongations of the core jacket continue up to a pointindicated in the diagram ,(Fig. 16) by the sudden downward bend in thecurve. Beyond this point, the structure of the jacket does not permitits substantial further collapse in diameter, but before this point isreached the jacket again grips the core.

The casing or jacket is capable of elastic elongation, after structuralelongation has nearly reached its maximum, in response to furtherapplication of loading stress. The elastic elongation is due in part toelastic stretch of the constituent filaments which make up the yarns,and in part to modification. in response to stress, of the twistimparted in preparing the individual yarns and in preparing the pliedyarns employed. A braided nylon jacket or casing, when subjected toloading stress, thus elongates elastically approximately 30% (ascompared With its length after structural elongation has substantiallyreached its maximum) before reaching the elastic limit. Thus, if throughsome unexpected circumstance, the load applied to the shroud is far inexcess of that which is normally imposed by the sudden opening of thecanopy, the. elastic resistance to stretch of the jacket provides afactor of safety such as to prevent the shroud from breaking. Fig. 16shows that the shroud continues elastically to elongate, butrelatively'slowly,

far beyond the point of application of the in-;

tended riding load ('7 or 11 pounds respectively) and the shroud isreadily capable of elasticelongation in response to the suddenly appliedload, due to the opening of the canopy (for instance of the order of 28pounds per shroud), without rupture either of the jacket or of the core.

Expressed mathematically, the completed core, made as above described,appears to have elastic.

characteristics as follows: Assuming that the core alone is capable ofelastic elongation. X at its elastic limit, it is normally elongated, inthe relaxed shroud, by an amount W which is less.

than X but greater than zero.' Preferably W is of the order ofapproximately 20% of X. The casin alone (of aninitial at rest length M.)is capable of a structural elongation 'byreason of the rearrangementofits braided st'randswhen subjected to tension, but without substantial'elaatic elongati'on of its constituent individual yarns. The casing iscapable of an additional elongation Z (approximately 30% of M-i-Y), byreason of the elasticity of its constituent yarns after its structuralelongation Y has ceased, for all practical purposes. The maximumelongation Y+Z of the casing issubstantially less than the maxi mumelongation Xof the core. When the shroud.

is subjected to load, the casing constitutes elastically stretchablelimiting means for determining the maximum elongation of the shroud,butthe core is sufliciently resistant to elongationto sustain the ridingload at an elongation of the core much less than X, and with the shroudextended substantially less than X (Y+Z) is the safety factor for thecore. Expressed arithmetically elongation of the core at the time ofhighest possible shock load is W+Y+Z and that elongation must besubstantially less than X, and the difference between (W+ Y-l-Z) and Xis the safety factor applying to the rubber core.

While herein the core or core threads are referred to as of rubber, itis to be understood that the core or core threads may be of any othermaterial, for instance, synthetic rubber, having substantially thestretch and elastic recovery characteristics of vulcanized naturalrubber: Moreover, while nylon has been referred to as a' desirablematerial for use inma king the jacket or casing, any material havingsimilar characteristics, particularly with reference to elastic stretchand recovery maybe employed;

The size and amount of yarn used in any given case depends upon theultimate breaking strength specified for the shroudto be made and theirdetermination is within the common, knowledge of those skilled in theart. Reducing'the number of picks per inch in the braided jacket tendsto produce a shroud of a shorter relaxed length and, conversely,increasing the numberv of picks per inch increases the relaxed length.The, relaxed or no-load length of lineis of concern only'in' maintaininguniformity for packing, but t'he stretched or riding load length isimportant since the proper functioning of the parachute is largelydependent-upon the proper length of the lines. While certaindesirable'materials and modes of.

procedurehave hereinbeen described and certain" examples have beengiven'as illustrative of the practice of the inventionpit is to beunderstoodthat the invention is broadly inclusive or all suchmodifications in materials, proportions and pro-- cedures' as fallWithin'the scope of'the. appended claims;

We claim 1. A- parachute shroud comprising a braided jacket and arubber-elastic core, the core comprising abundle ofsubstantially"parallel elastic thr'ea'ds firmlybound together" atopposite ends m-ally held stretched, intermediate said end bind;ingaby-th'egrlpof'the jacket whenthe shroud-- is unloaded,-;the normalelongation of -the core 3 threads being less than their elongation whenthe shroud is supporting ther'idingdoad. v

2. A parachute shroud comprising a braided jacket, a-rubber-elastic coreand relatively inelastic terminal cords united; respectively,totheopposite ends-of the, core, the jacket coVer-inglthe masins t:hemwith th conn cti cards,

ii at shtl b a dedi c e 1, x' lfil met odp making elastica lyst etclable .-pa1'achute:shrouds sWh'jQh comprises preparing rubber-elasticcore units each of a len th a p op ate :io u in mak ng-a sin p ra hutesh oud necti a p ura y of sa c e-units -in se"ries by me yns Ofsubstantially inel stic cords, subj cting he .-,c,onn cted se ies f coreunits to tension such as to stretch them to an amount not substantiallyexceeding 20% of their elongation at the elastic limit, and, while -gthecore units thus stretched, braiding a Jack t b u t mlg. Ifhat method ofmaking elastica1lystretchable (parachute shrouds which comprises assteps preparing rubber-elastic core units each of a lengthiappr;o'nriate for use in making ,a single parachute shroud, vconnectinga plurality of said core units in series by means of relatively inelas-.ticeords, subjecting the consequent series of core :units to tensionsuch as toelongateeach unit to at :l;eas t doubleits initial length ,butless than its maximum elongation at the elastic limit of the,eonstituent rubber threads, and braiding a jacket of textile yarn-sabout the core units and their z on nsc r si .115. Thatimethod of makingelasticallystretchable parachute shrouds which comprises as stepspreparing rubber elastic core units each of a length appropriate for usein making a single foaifachute shroud, connecting a plurality of saidcore units in}[series lziy means of relatively inelastic eordssubjectingthe connected series of core,units lto -tensionsuch'asto elongate eachunit to at least onehalf its maximum elongation ,at the elastic limit ofthe constituentrubber threads,,and braidinga jacket ,of nylon yarnsaboutthe extended corelun'its-and theinconneotingicords and permittingthecompositestrand .to relax.

16) That method. of making elastically stretchable parachute shroudswhich comprises as steps prepa i g ubbe astic core un t eac o a lengthappropriate for use in ,making a single parachute shroud, connecting a,plurality of said Fl e un t in s e by m anso sub t tia ly inextensiblecordssubjecting each core unit of the series to tension such as toelongate it ,to from Pil -half to two-thirds of its maximum elongationat the elastic limit ,of ;the {constituent threads, br idin ja k t off-non rn about thmextended core units and their connecting cords, severingthe Jacket and the connecting cards at points approximately mideway:betweenthe ends of adjacent core units, and fusing :the nylon yarnsv ofthe jacket at the points of severence. That e h d of ma g e asticalltretuhable parachuteshrouds which com rises as steps preparingrubber-elastic core units each of .a length appropriate for use inmalging ,a single parachute shroud thy disposing in substantiallyparallel relation a plurality of rubber-elastic core threads, in numbersuificient to constitute a desired core, tensioning the core threads,and applying to the tensioned core threads elastic constrictive bindingsat intervals spaced apart a distance which, after the core unit hasbe'en permitted to relax,-is substantially equal tothe length of thedesired core unit.

;1 8. '-1lhat method of making elastically stretch- ?b P achute shroudswhich comprises as steps preparing rubber-elastic pore units each of 'alength appropriate for use in making a single parachute shroud bydisposing in substantially parallel relation a plurality ofrubber-elastic core .l y s retchable I parachute shrouds -;Whi, ?h-con1pi?ises as steps r r n -rub er-.elast c are nits sac; n th p 99 F91 p'11156 in s l g liill P i parachute shroud by disposing in; beta-n 1 yparallel relation a plurality,qirubbereelastic core t ead nln mber suficient t con t tuteith,e.dee sired core an y fi fi f gt 9 ifi $.3YQ E--9Q units, equallytensioning the several eere threads, nd bindingtogether .the several threads with wrappings of tensioned elasticthread, successive wrappings being spaced apart -a distance, er the coreunit has been permitted to relax, approxim i th n h h or u it n o a s nle sh ud, ach "wrappin ompr s n a pai s a d; i dependent-sayings pt t erubber-elastie binding thread.

2 h z t od mak n ie ti ell si e eh able parachute shrouds whichcomprises sis steps preparing rubber-elastic core units by dis-posing ins n a l a all l e ation a plura t =9; rubber-elastic,core threadsinn-umber iiicie i constitute the desired-coreand of a length togfo nseveral core units, equally tensioning the several core threads andbinding together- -the several threads with ,wrappings of t nsionedelastic thread, successive wrappings be ng spaced apart adistance,whenthe coreiunit'relaxed appro mating the en h 0 a 9 m u it-fer asshroud, each wrapping comprising two independent servings of the.rubbereelastic thread Spa ed-a ar idistanc a pr xima ely e e-e shth incwhen th ore thread a e a ed,

2 That method of mak ng elastically stretchable parachute shrouds whichcomprises as steps R i -l 'Qfl O 9 :llll @5119 .n i su t n l l Wmil llil? 0! rubber-elastic core threads,innurnbensuificientrto constitute thedesired ,core and 117i a g form several core units, egually tensioningthe several core threads, appl in t t e t nsi ned core threads elasticconstrictivebindingset inter- .vals spa ed ap r a dis app which the c ehas bee permitt towelax sub ally equal to the length of the desiredgcore unit, each bind,- ing pon s ing 9 wo indep ndent :pa-rts spaced adistance pf vthe ,crder of one1half;of;an,-inch, :and thereafter.seuering-the parallel ,co zewthreads .at nts int rm di t s aceiin eendentpa s preach respectiye binding; thereby .to provide elasticallystretchable core iunits leach having its constituent threadsxbounditightlyitogether at as ppposite d 22. That method of making elasticallystretchable parachute shroud which comprises as steps aproyiding:rubbereelastic :core units each ofa len th appropriate for use inmaking a-sifngle arachute shroud,- each unit comprising :a bundle ofsubstantially parallel rubber-elastic threads and each unit:havin'g-aconstrietive-"bits opposite ends, uniting said s ream i'Zoyiloopinga relatively inelastioc'ord itran y through the bundle ofcore'threads of adjacent units, at points inwardly of and adjacent totheir end bindings, uniting the ends of each of said cords,constrictively binding the legs of each cord loop to the respective endbindings, and encasing the connected series of units with theirconnecting cords in a tubular braid.

f 23. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing rubber-elastic core units bydisposing rubber-elastic threads in parallel relation, tensioning thecore threads and applying constrictive bindingsto the tensioned threadsat distances apart such that, after the core threads have been permittedto relax, the bindings are spaced approximately the length of thedesired unit, severing the core threads at the locations of the severalbindings, thereby to provide core units each having a binding at eachend, dividing the core threads at each end of the unit into twosubstantially equal groups, passing a connecting cord between saidgroups and arranging it to form a loop whose'legs are parallel to theend binding of the unit, and cons'trictively securing the legs of theloop to said end binding.

24. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing rubber-elastic core units bydisposing rubber-elastic threads in parallel relation, tensioning thecore threads and applying constrictive bindings to the tensioned threadsat distances apart such'that, after the core threads have beenpermittedto relax, adjacent bindings are spaced approximately the lengthof the desired unit, severing the core threads at the locations of theseveral bindings, thereby to provide core units each having a binding ateach end, dividing the core threads at each end of the unit into twosubstantially equal groups, passing a connecting cord between saidgroups and arranging the cord to form a loop whose legs are parallel tothe end binding of the unit, and wrapping a tensioned rubber-elasticthread about the, parallel legs of the loop about the end binding,thereby to anchor the cord to the bound end of the core unit.

25. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing rubber-elastic core units bydisposing rubber-elastic threads in parallel relation, tensioning thecore threads and applying constrictive bindings to the tensioned threadsat distances apart such that, after the core threads have been permittedto relax, the bindings are spaced approximately the length of thedesired unit, severing the core threads at the locations of the severalbindings, thereby to provide core units each having a binding at eachend, dividing the core-threads at each end of the unit into twosubstantially equal groups, passing a substantially inextensibleconnecting cord between said groups andarranging the cord to form a loopwhose legs are parallel to the end binding of the unit, and applying anelastically constrictive casing to the parallel-legs of the cord loopand to the end binding, said constrictive casing tapering in diameter,its smaller end embracing the legs of the loop alone.

, 26. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing rubber-elastic core units bydisposing rubber-elastic threads in parallel relation, tensioning thecore threads and applying a constrictive binding to the tensionedthreads, severing the core threads at the locations of the bindingthereby to provide a core unit having a binding at its end, dividing thecore threads at the bound end of the unit into two substantially equalgroups, passing a connecting cord between said groups and arranging thecord to form a loop whose legs are parallel to the end binding of theunit, and wrapping a tensioned rubber-elastic thread about the parallellegs of the cord loop and about the end binding, said wrapping extendingbeyond the end of the binding and tapering in diameter, its smaller endembracing the legs of the loop only.

27. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing rubber-elastic core units bydisposing a plurality of rubber-elastic core threads in ubstantiallyparallel relation, binding the tensioned threads together at distancesapart approximately such that after the core threads have been permittedto relax the-bindings are spaced apart the length of the desired unit,each binding comprising two independent wrappings of tensionedrubber-thread spaced apart a distance of the order of one-eighthinch,severing the core threads between the wrappings of each binding therebyproviding independent core units, separating the core threads of eachunit adjacent to its end bindings into two groups each of substantiallythe same number of threads, passing a cord between the two groups at theapproximate ends of two adjacent core units, uniting the ends of thecord at a point intermediate the end of the adjacent units, and wrappingthe legs of the cord loops where they lie parallel to the end bindingsof the respective adjacent units with servings of rubber-elastic threadto form constrictive casings for said end bindings and for the legs ofthe cord loops adjacent to said bindings.

28. That method of making elastically stretchable parachute shroud whichcomprises as steps preparing a rubber-elastic core by marking asubstantially relaxed rubber-elastic core strand at regularly spacedintervals, tensioning the strand while encasing it in a braided jacket,and adjusting the tension during braiding by reference to the spacing ofsaid marks, thereby to insure a uniform per cent elongation of thestrand, and braiding tensioned textile yarn to form a jacket whichtightly embraces the core,

29. That method of making elastically stretchable parachute shroudswhich comprises as steps preparing a rubber-elastic core by disposingsub-.- stantially relaxed rubber-elastic core threads in substantiallyparallel relation, marking one at least of said threads at regularlyspaced intervals, applying tension to elongate the several threads whileencasing them in a braided jacket, and adjusting the tension duringbraiding so as to maintain a substantially uniform spacing of said marksduring the braiding operation, and braiding tensioned textile yarns toform the jacket about the core.

ROBERT T. DAWES. FRANK TAYLOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENT Severance June 17, 1947

